1. Field of the Invention
This invention relates to a pulse oximeter probe that detects the pulsation or throbbing of blood flowing through a blood vessel in the living body so as to measure the oxygen saturation of blood and other blood-related parameters. The invention relates particularly to a pulse oximeter probe of a type that is to be attached to the ear of a subject.
2. Related Art
Conventional pulse oximeter probes which are to be used for measuring the oxygen saturation of blood and other blood-related parameters in the living body are available in two types depending on the mechanism for detecting the pulsation of blood flowing through blood vessels, i.e., by light transmission through the probe that is attached to a subject's finger, leg or earlobe or by light reflection from the probe that is attached to the forehead of the subject having a comparatively large amount of blood circulation.
A problem with the type of probe that is to be attached to a subject's finger or leg is that the subject is no longer free to use both hands or finds difficulty in walking. Furthermore, it is difficult for the analyst to acquire consistent data. On the other hand, less inconvenience will be caused to the life of the subject if the probe is attached to his earlobe.
A conventional pulse oximeter probe of the type that is to be attached to the earlobe is typically in the form of a clip. As shown in FIGS. 13 and 14, the probe comprises generally a pair of holding members 21 and 22 that are connected together at an end in such a way that they can pivot on a shaft 23. The holding members 21 and 22 are furnished with a light-emitting device 24 and a light-receiving device 25, respectively, in such a way that they are in a face-to-face relationship. The shaft 23 is fitted with a leaf spring (not shown) that urges the devices 24 and 25 to pivot in a direction in which they approach each other. The probe generally indicated at 27 can be attached to the earlobe 26 of a subject by holding it with the holding members 21 and 22.
However, the conventional oximeter probe of the clip type which is constructed in the manner just described above has two major drawbacks. First, the holding members 21 and 22 have to compress the earlobe 26 so as to detect the pulsation of blood flowing in the compressed area but, then, the quantity of blood circulation decreases to lower the precision of measurement. Second, the probe 27 which is attached to the earlobe 26 is liable to movements and, hence, errors due to the movement of the earlobe are most likely to occur if measurements are done while the subject is walking.